Process for curing halogenated butyl rubber with a bivalent metal oxide and an organic polythiol compound, and product obtained thereby



3,041,304 Patented June 26, 1952 PROCESS FOR CURING HALOGENATED BUTYLRUBBER WITH A BIVALENT METAL E AND AN ORGANIC POLYTHIOL COMPOUND, ANDPRODUCT OBTAINED THEREBY Irwin J. Gardner, Roselle Park, Samuel B.Robison,

Roselle, and Henry S. Makowski, Carteret, N.J., assignors to EssoResearch and Engineering Company, a corporation of Delaware No Drawing.Filed Oct. 23, 1958, Ser. No. 769,100

13 Claims. (Cl. 26041.5)

The present invention relates to rubbery compositions containinghalogenated low unsaturation polymers as well as the preparation andvulcanization of such compositions. More particularly, it relates toimproved methods for curing rubber containing a substantial amount ofhalogenated low unsaturation polymer with minor amounts of substanceshaving more than one thiol group.

Thiol compounds, i.e. compounds containing SH groups, have heretoforebeen employed to form crosslinks between molecules of high unsaturationrubbers, such as 'butadiene-styrene rubber (GRfiS), and monoithiols havebeen reacted with which polymers in olefin type studies as well as inpreparation of modified rub "bers, e.-g. modified polybutadiene. Whilethese compounds have been shown to have some effect as crosslinkingagents, they have never been widely accepted as curing agents for highunsaturation rubber because of many difliculties which have beenencountered. More over, when these compounds have been employed in anattempt to vulcanize low unsaturation rubber, such as butyl rubber, theresult has been that the rubbers are either not cured or are of a poorquality. Therefore, these polythiol compounds are not consideredsuitable curing agents for butyl rubber.

It has now been discovered that polythiol compounds will curehalogenated low unsaturation rubbers and produce vulcanizates havingexcellent physical, dynamic, flexing and chemical properties. Forinstance, a major proportion of halogenated butyl rubber may be curedwith minor proportions of various polythiol organic c0mpounds underordinary conditions well known in the art.

The present invention is not restricted to any particular polythiolorganic compound since the critical feature is the combination of anorganic compound having more than one thiol group attached to it andhalogenated low unsaturation rubber. While it is necessary that thethiol compound contain at least two thiol groups, additional thiolgroups, as well as other reactive or unreactive groups, may be attachedto the basic carbon chain or carbon ring structure. For instance,besides the thiol groups there may also be present oxygen-containinggroups such as alcohols, acids, esters, aldehydes, ketones, etc. Most ofthe polythiol compounds coming Within the scope of the invention containfrom 130 or more carbon atoms and may generically be classified aspolythiol alkanes, polythiol alkenes, polythiol cycloalkanes, polythiolcycloalkenes and derivatives thereof. While the polythiol compounds mayhave as many as -6 thiol groups, the preferred compounds contain from2-4 such groups.

A generic formula that may be used to define the dithiol compounds whichcome within the purview of the invention is as follows:

wherein H is hydrogen; S is sulfur; and R is an alkane, alkene,cycloalkane, cycloalkene or derivatives thereof containing from 1 to 20or 30 carbon atoms (preferably a C to C alkyl or a C to C eycloalkene).

Some specific polythiols that may be used in the practice of the presentinvention include:

Bismercaptomethyl- 1,2,3 propane trithiol m-benzene The preferredhalogenated low unsaturation compound is halogenated butyl rubber. Butylrubber is a polymer which contains about to 99.5 wt. percent of a C to Cisoolefin, such as isobutylene, and about 15 to 0.5 wt. percent of amultiolefin containing 4 to 14 carbon atoms, and preferably about 4 to 6carbon atoms. While the preferred multiolefin is isoprene, otherconjugated diolefins such as butadiene-1,3, dimethylbutadiene andpiperylene may be employed. Butyl rubber or GR-I rubber (GovernmentRubber-Isobutylene) generally has a mole percent unsaturation between0.5 and 15 and a viscosity average molecular weight of from about200,000 to 1,500,000 or more. Its preparation is described in US. Patent2,356,128 issued to R. M. Thomas et a1. and elsewhere in the literature.

The halogenated butyl rubber most suitable for the purposes of thepresent invention is butyl rubber Which has been carefully halogenatedso as to contain at least 0.5 wt. percent (preferably about 1 wt.percent) of combined halogen but not more than about X wt. percentcombined chlorine or 3 X wt. percent of combined bromine wherein:

and

L=mole percent of the multiolefin in the polymer M =molecular weight ofthe isoolefin M =molecular weight of the multiolefin M =atomic weight ofchlorine or bromine Restated, there should :be at least about 0.5 weightpercent of combined halogen in the polymer but not more than about oneatom of chlorine or 3 atoms of br mine combined in the polymer permolecule of multiolefin present therein; i.e., not more than about oneatom of combined chlorine or three atoms of combined bromine per doublebond in the polymer.

Suitable halogenating agents which may be employed are gaseous chlorine,liquid bromine, alkali metal hypochlorites, sodium hypobromite, C to Ctertiary alkyl hypochlorites or hypobromites, sulfur chlorides orbromides (particularly oxygenated sulfur chlorides or bromides),pyridinium chloride perchloride, N-bromo-succinimide, iodinemonochloride, alpha-chl-oroacetoacetanilide, tri bromophenol bromide,N-chloroacetamide, beta-bromo-methyl phthalimide, N,N'-dimethyl-5,5dichloro or dibromo hydantoin, and other common halogenating agents.

The halogenation is generally conducted at above 0 to about C.,advantageously at about 0 to 65 C., preferably at about 20 to 50 C.(room temperature being satisfactory), depending upon the particularhalogenation agent, for about one minute to several hours. Anadvantageous pressure range is from about 0.5 to 400 p.s.i.a.;atmospheric pressure being satisfactory. The halogenation conditions areregulated to halogenate the rubbery copolymer to the extentabove-mentioned.

The halogenation may be accomplished in various ways. For instance,the'solid copolymer may be halogenated per se. Another process comprisespreparing a solution of the copolymer as above, in a suitable inertliquid organic .(eg. 70 C.).

erties desired in the vulcanizate.

solvent such as a C to C or preferably a C to C inert hydrocarbon orhalogenated derivatives of saturated hydrocarbons, examples of which arehexane, heptane, naphtha, mineral spirits, cyclohexane, alkylsubstituted cycloparaflins, benzene, chlorobenzene, chloroform,trichloroethane, carbon tetrachloride, mixtures thereof, etc., andadding thereto gaseous chlorine, liquid bromine, or other halogenatingagent, which may optionally be in solution, such as dissolved in anyinert hydrocarbon, an alkyl chloride, carbon tetrachloride, etc.

The concentration of the butyl rubber in the solvent will depend uponthe type of reactor, molecular weight of the butyl rubber, etc. Ingeneral, the concentration of a butyl rubber having a viscosity averagemolecular weight of about 200,000 to about 1,500,000, if the solvent isa substantially inert hydrocarbon,-will be between 1 and 30% by weight,preferably about 5 to 2%. If chlorine gas is employed to chlorinate sucha rubbery solution, it may also be diluted with up to about 50 times itsvolume, preferably about 0.1 to 5.0 times its volume of an inert gassuch as nitrogen, methane, ethane, carbon dioxide, etc.

The resulting halogenated butyl rubber polymer may be recovered invarious manners. The polymer may be precipitated with acetone or anyother known non-solvent for the butyl rubber and dried under about 1 to760 millimeters or higher of mercury pressure absolute at about to 180C., preferably at about 50 to 150 C.

Other methods'of recovering the halogenated butyl rubber polymer fromthe hydrocarbon solution of the same are by conventional spray or drumdrying techniques. Alternatively, the halogenated butyl rubbercontainingsolution may be injected into a vessel containing agitated water heatedto a temperature suificient to flash off the hydrocarbon solvent andform an aqueous slurry of the halogenated butyl rubber. The halogenatedbutyl rubber may then be separated from this slurry by filtration, driedand recovered as a crumb or as a dense sheet or slab by conventionalmilling and/or extruding procedures. The halogenated copolymer formedadvant-ageously has a viscosity average molecular weight between about200,000 and 1,500,000 and a mole percent unsaturation of between about0.5 to 15.0, preferably about 0.6 to 5.0.

The quantity of polythiol organic compound, or mixtures thereof, blendedwith the halogenated butyl rubber and other ingredients will, of course,depend on the prop- Thus, the amount of polythiol organic compoundemployed may range from .as little as 0.1 part by weight per 100 partsby weight of rubber (phr.) to as much as 15 phr. or more. However, inmost instances it is necessary to use at least about 0.5

phr. of the polythiol organic compound in order to ob- I tain avulcanizate having good properties. Moreover, for polythiol compoundshaving molecular weights below 300, it is generally desirable to use notmore than 5 or phr. of polythiol. Since it is believed that thepolythiols react with the halogen contained in the low unsaturationpolymers and since the halogen content of the polymer may vary, it isusually best to use from about 0.25 to 0.75 mole of polythiol compoundfor each mole atom of halogen in the polymer.

While the polythiol compounds of the present invention are suitablecuring agents in themselves, it is sometimes desirable to include in therubber recipe a minor amount, say 0.5 to 10 phr., of a bivalent metaloxide, e.g. tin oxide, lead oxide and especially zinc oxide. It has beennoted that metal oxides, the metal portion of which is a low meltingmetal selected from groups Hi3 and IVA of the Periodic Chart, (LangesHandbook of Chemistry, 8th edition), not only co-cure the halogenatedlow unsaturation rubber but also appear to accelerate and enhance thecuring action of the polythiols themselves. It is believed that thepolythiol reacts with the metal oxide to produce a polymercaptide whichwill rapidly react with labile halogen atoms to effect cross-links at arate considerably higher than the polythiol itself. Therefore,

where high tensile strength rubber compounds are needed, it is advisableto employ from about 1 to 5 phr. of metal oxide.

Prior to vulcanizing the halogenated low unsaturation rubber with thepolythiol organic compounds of the present invention, in the presence orabsence of zinc oxide, conventional amounts of fillers such as carbonblack, clay, etc. may be compounded with the rubber. For instance, therubber recipe may include from 30 to 70 phr. of carbon black or finelydivided siliceous material, 0.1 to 10 phr. of an accelerator, such asbenzothiazyl disulfide, tetramethyl thiuram disulfide orZ-mercaptoimidazoline, about 0.1 to 5 phr. of stearic acid, conventionalamounts of hydrocarbon extender oils and plasticizers as well as minoramounts of tackifiers.

The rubber stocks compounded according to the present invention mayinclude, in addition to those things mentioned above, other polymerssuch as butadiene-styrene polymer, natural rubber, polyisobutylene,polyisoprene, polychloroprene, butyl rubber and reclaimed butyl rubber.It is only necessary to have a sufiicient quantity of halogenated lowunsaturation rubber in the recipe to produce a vulcanizate having thephysical properties required for the particular article which willcontain the vulcanized rubber. Moreover, it may be desirable in certaininstances to have other curing agents present, such as sulfur, sulfurcompounds, and dimethylol-paraor metaalkyl substituted phenol resins.These ingredients may be used in conventional quantities.

The halogenated, low unsaturation rubbers compounded according to thepresent invention may be used in many articles that are madewholly orpartially with rubber. For example, they may be employed in tires,curing bladders and bags, hoses, wire insulations, conveyor belts, etc.They may be emulsified in an aqueous system or dissolved in an organicsolvent, such as hexane, and used to treat fabrics, especially cotton,nylon or rayon tire cords. The latices and cements prepared with rubbercompounded in accordance with the present invention may be used toadhere various fabrics or metals, as well as various rubber stocks,including stocks containing natural rubber and butadiene-styrene rubber.In the case of latices, when bonding fabric to rubber, it is generallyadvisable to have a minor amount of a phenolic-aldehyde resin, such asresorcinol formaldehyde resin, in the dip. Sometimes, it is desirable toinclude in the clip a small quantity of the polytluol organic compoundsof the present invention. The polythiols may be used in combination withthe resin or in lieu thereof.

The rubber stocks compounded according to the present invention may bevulcanized according to processes well known in the art. For instance,the compounded rubber may be press cured or steam cured at elevatedtemperatures, say from 250 to 400 *F., for from a few minutes up toseveral hours. It is preferable in most instances to carry out thevulcanization at a temperature between 250 and 350 F. for from 5 tominutes. The vulcanization time is usually shorter when highertemperatures are employed and longer when lower temperatures are used.Relatively speaking, the cure is generally quite rapid and the physical,chemical, dynamic, etc. properties of the vulcanizate are superior tothose obtained with zinc oxide alone or combinations of zinc oxide andaccelerators, such as tetramethyl thiuram disulfide. Some of thepolythiol organic compounds, especially the higher alkyl and aromaticderivatives when compounded according to the present invention, producerubber stocks which have a Mooney Scorch as high as 30 minutes or more(Small Mooney-minutes to cause a 5 point rise) at 260 F.

As already mentioned, the polythiols do not cure butyl rubber. This isdemonstrated by an experiment in which parts by weight ofisobntylene-isoprene butyl rubber having a mole percent unsaturation of1.5 to 2.0 and a viscosity average molecular weight of about 500,000 wascompounded with 50 parts by weight of HAF black, 1

part by weight of bismercaptomethyl-m-xylene and 3 parts by weight ofzinc oxide, and heated for /2 hour at 307 F. It was noted that thecompounded rubber was 30 minutes at 340 F. The physical properties ofvulcanizates are shown in Table III.

not cured at the end of the /2 hour period. Table III The followingexamples are given in order to illustrate 5 the practice of the presentinvention and show some of the Properties B improved properties obtainedby curing halogenated, low unsaturation rubber with polythiol organiccompounds. 15 15 Throughout the examples reference will be made tochlorinated and brominated butyl rubbers. The chlorinated 388% ,1333%;B12 228 328 323 ggg butyl rubber was prepared by chlorinating acopolymer p 2,5 2,320 2, 220 2,270 containing about 97 wt. percentisobutylene and 3 Wt. Elongmmnpment" 400 560 500 percent isoprene whichhad a viscosity average molecm ular weight of 486,000. The chlorinatedcopolymer ob- The data lahles Show that W Small tained contained 1.12wt. percent chlorine and had a 15 amounts of 1,5 P h glycol f Pviscosity average molecular weight of 460,090 The acetate are used 1ncomunctlon with zinc oxide (reclpes 'brominated butyl rubber wasprepared from a copolymer A and B) they PrPduce Vulcahlzates, WhetherPrepared containing about 97 wt. percent isobutylene and 3 wt. at h lowand hlgh tFrhperathresgwhlch grealer percent isoprene which had aviscosity average molecular @hsfle trehgths than vhlcahlzates h h wlthweight of 491,000. The brominated copolymer contained elthhr Zmc oxlfiealone (recipe D) Wlth Zlhc oxlde and 2.49 Wt. percent bromine and had aviscosity average (Tempe Mhreoveri the cure rates for the molecularWeight equal to that of the original copolymer. dlthlol compouhdedhhlonhated butyl rubber h f than those obtained With the TMTDS and/orzinc oxide EXAMPLE 1 recipes. This is reflected in the greatly improvedmoduli Chlorinated butyl rubber wa compounded ith i of the dithiolvulcanizates in contrast to those of the oxide and one of the following:1,5 pentane dithiol, TMTDS nd Zinc O d C res. glycol dimercaptoacetate,or tetramethylthiuramdisulfide mples of recipes A, B, C and D that W rcured f r (TMTDS). Since TMTDS is presumed capable of formminutes at 307F. were aged for 168 hours at 250 ing two cross-links between polymermolecules per mole- F. to comp-are the eflect of heat on thevulcanizates. The cule of TMTDS and the aforementioned dithiols are be-30 physical properties of the vulcanizates after aging at the lievedcapable of producing only one such cross-link, two a rementi nedelevated temperature are Set forth in moles of the dithiols were usedfor each mole of thiuram Table IV. disulfide in the following recipes:Table IV Parts by Weight Properties A B C D Ingredients A B o D 200%Modulus, p.s.i 760 1,170 520 270 300% Modulus, p.s.i 1,280 880 460Tensile, p.s.i 1,560 1,680 1,160 790 Chlorinated butyl rubber 100 100100 100 Elongation, percent 3 2 380 480 SRF carbon black Stearic acidg;- The results 1n Table IV show that the vulcanizates ob- 5 1 1 figggfgggjjjjj I: tained with recipes A and B retain [their physical prop-Temmethylthihmmdislhhde erties better than those prepared from recipes Cand D.

Each of the above non-rubber ingredients was added to the chlorinatedbutyl on a rubber mill at 80 to 90 F. in the conventional manner. Asample of each chlorinated butyl rubber so compounded was cured for 15or 30 minutes at 307 F. The physical properties of the vul- EXAMPLE 2The recipes employed in Example 1 were repeated with canizates are setforth in Table I. the exception that the concentrations of the dithioland Table I A B o D Properties 15 Min. 30 Min. 15 Min. 30 Min. 15 M111.30 Min. 15 Min. 30 Min.

200% Modulus, p.s.i 1,160 1,010 1,140 1,300 680 000 400 430 300%Modulus, p.S.l 1, 900 1, 010 1, 900 1, 030 1,180 1, 220 870 840 Tensile,p.s.i 2, 240 2,270 2,280 2,060 2,000 2,100 1,300 1,880 Elongation,percent- 380 380 390 310 500 500 550 570 Samples of B and C above werecured for 45 and 90 minutes at 250 F. The physical properties of thevulcanizates are shown in Table II.

Samples of recipes B and C above were also cured 15 and 75 30 and 45minutes at 307 the disulfide were increased. Hereafter, these recipesshall be referred to as recipe A B and C Thus, the amount of 1,5 pentanedithiol was increased trom 0.56 part by weight to 1.13 parts by weight.Likewise, glycol dimercaptoacetate and TMTDS were increased to 1.83 and1.0 parts by weight, respectively. The Mooney scorch time for recipe Aat 260 F. was greater than 30 minutes (time required to cause a fivepoint rise-small Mooney). Receipe B had a Mooney scorch time which wasmore than twice that obtained with recipe C (1 phr. oftetramethylthiuramdisulfide). Thus, the polythiol com-pounds produce aless scorchy rubber stock than that obtained with zinc oxide andtetramethylthiuramdisulfide. Samples of recipes A B C and D were curedfor 15,

Table V A! B1 C1 D Time (minutes) 15 so 45 15 30 45 15 30 45 1s 30 45Properties:

200% Modulus, p.s.i 1,020 1,170 1,130 1,130 1,340 1,240 720 790 730 380460 430 300% Modulus, p.s.i 1, 920 2,000 2,007 2,200 1,240 1,300 1,280840 940 880 Tensile, psi 2,200 2,080 2,160 2, 330 2,210 1,870 s 1, s901, 920 1, 370 1,870 1,700 Elongation, percent 345 315 325 350 375 27 47050 595 525 580 The above data show that recipes A and B were sub-Samples of each of the vulcanizates in Example 4 were stantially curedafter curing for only minutes while evaluated with the GoodrichFiexometer (ASTM Standthe vulcanizates obtained with recipes C and Dwere ards on Rubber Products D623-41T Method A). The either not fullycured or possessed inferior physical prop- 15 following conditions wereemployed in evaluating the flexerties. Samples of the vulcanizatesobtained afiter curing ing properties of each of the vulcanizates. Theload was for 30 minutes at 307 F. were aged for 168 hours at li8 l'bs.per square inch, the stroke was 0.25 inch and the 250 F. and theirphysical properties were re-evaluated. frequency was 32 cps. The resultsof the test which was The data obtained are in Table VI. carried out atan oven temperature of 100 C. are given Table VI in Table VII.

Properties A; k B1 01 i D Table VII 200% Modulus, p.s.l 750 1,100 570210 300% Modulus, p.s.i 1, 210 1,720 1110 3-30 Tensile, p.s.i 1, 260 1,840 1, 140 440 Elongation, Percent... 320 320 385 490 Permanent DynamicTempero- Appear- Vulcanizate rift, turc Rise, ance I Percent Percent C.The results show that curing with polythiols in accordance with thepresent invention enhances the heat aging properties of halogenatedbutyl rubber vulcanizates. Glycol 0) 2.3 0.0 24 Excellent.dimercaptoacetate produced a vulcanizate that was very 20 0'0 26 D0. 1.00.0 22 Do. efiective in this regard. g g g 8 23 g 22 0. EXAMPLE 3 0.80.0 19 Do. Example 1 was repeated using higher concentrations 24 ofdithiol and disulfide in recipes A, B and C. The corresponding recipesshall hereafter be referred to as A B C B and C Thus, recipe A contained2.26 parts by weight of 1,5 pentane dithiol, recipe B contained 3.50parts by weight of glycol dimercaptoacetate, recipe C contained 2 partsby Weight of tetramethylthiuramdisulfide, recipe 13;, contained 5.25parts by weight of glycol dimercaptoacetate and recipe C contained 3parts by weight of TMTDS. The recipes were cured for various periods oftime at 250 F. (45 and 90 min), 307 F. (15 and min.) and 348 F. (5 and15 min). The vulcanizates obtained with the polythiol compounds weregenerally equivalent in physical properties to those obtained with thecombination of TMTDS and zinc oxide and superior to that obtained withzinc oxide alone. The physical properties of the vulcanizates obtainedwith recipes B were generally inferior to that obtained with recipe BThis indicates that there exists an optimum concentration below about 5phr. of low molecular Weight dithiol for vulcanizates which have hightensile strengths and moduli.

EXAMPLE 4 Chlorinated butyl rubber was compounded in the followingrecipes on a rubber mill at 80 F. and vulcanized for 30 minutes at 307F.:

EXAMPLE 5 The dynamic properties of the vulcanizates prepared in Example4 were evaluated. The method employed is described in ASTM Standards forRubber Products D945- 4ST (Modified Yerzley). The results obtained areset forth in Table VIII.

Ingredients Chlorinated butyl in her SRF carbon black Stearic acid. Zincoxide" Tetramethylthiuramdisulfide (TMTD S) 1,2 ethane dithiol-.

1,3 propane flithinl 1,4 butane cilthi0l- 1,5 pentane dl inlBls-mercaptomethylmetaxylene Glycol dlmereaptoacetate Table VIII Abs.Damp. K. Dynamic Relative Vulcanizate 10- poises Modulus 10- Damping,

cps. dynes/cm. Percent The dithiol cured vulcanizates, especially thoseobtained with higher molecular weight dithiol compounds, have decidedlylower percent relative damping (20 to 25% lower) without a significantincrease in dynamic modulus. EXAMPLE 6 The vulcanizates prepared inExample 4 were cut in the shape of dumb-bells that were 0.75 inch thickand 0.25 inch wide at the narrowest part, stretched 50% at roomtemperature for /2 hour and then placed in a closed vessel whilestretched and there exposed to air containing 0.2 volume per cent ozone.The times required for each The data in Table IX show that in every casethe dithiol cured vulcanizates were more resistant to the attack ofozone than the TMTDS cured rubber (recipe F). The glycol dithiolvulcanizate, the most resistant vulcanizate to ozone, lasted almostthree times as long as the TMTDS vulcanizate control in this test.

EXAMPLE 7 The vulcanizates prepared in Example 4 were evaluated forvolume swell in cyclohexane. Each vulcanizate was submerged incyclohexane for 48 hours at 25 C., blotted dry and Weighed in a sealedvessel of known weight. The percent weight increase was determined foreach vulcanizate since this is an indication of the crosslink density ofthe vulcanizate. The results which are given in Table X show that inevery instance the dithiol vulcanizates have a smaller weight increasethan that ob tained with the vulcanizate prepared with TMTDS and zincoxide or zinc oxide alone curing systems. The superior volume swellmeasurements obtained with the dithiol vulcanizates are in agreementwith the high moduli, better aging properties and superior dynamicproperties generally found with the dithiol in these vulcanizates.

Table X CYCLOHEXANE TES'IVULCANIZATE WEIGHT INCREASE Vulcanizate PercentWeight Increase 10 EXAMPLE 8 One hundred parts by weight of chlorinatedisobutylene-isoprene butyl rubber, containing 1.28 wt. percent combinedchlorine, having an average viscosity molecular weight of 571,000 and amole percent unsaturation of 0.55, was compounded with 50 parts byweight of HAF carbon black and one part by weight stearic acid. Onehundred parts by weight of the compound chlorinated butyl rubber wasblended with 2.43 parts by weight of glycol dimercaptoacetate andportions of the blend were cured for and 90 minutes at 307 F. Theoriginal and heataged properties of these vulcanizates are given 4 inTable XI.

Table XI ORIGINAL PROPERTIES Cure Time 60 Min. 90 Min.

300% Modulus 350 420 Tensile, p.s.i. 540 720 Elongation, percent 655 695PROPERTIES AFTER AGING 168 HOURS AT 250 F.

300% Modulus 960 1, 150 Tensile, p.s.i 1,090 1, 400 Elongation, percent355 365 PROPERTIES AFTER AGING 16 HOURS AT 380 F.

300% Modulus 360 360 Tensile, p.s.i 420 520 Elongation, percent 230 280EXAMPLE 9 One hundred parts by weight of brominated butyl rubber,described above, was compounded with 50 parts by weight of SRF carbonblack and one part of stearic acid. Portions (151 parts by weight) ofthe compounded brominated butyl rubber were. compounded with variouscuring agents in the amounts shown below:

Table XII Recipes M N O P Q R S Masterbatch; 151 151 151 151 Glycoldimercaptoacetate 0. 88 Durenedithiol 0.99

TMTDS 1,5 Pentaneeithiol Zinc Oxide Recipes M to R were cured for 15 and30 minutes at 307 F. and recipe S was cured for 60 and minutes at thesame temperature. The properties of the brominated butyl rubbervulcanizates are given in Table XIII.

Table XIII ORIGINAL PROPERTIES Recipes M N O P Q. R S

Cure Time (Min.). v 15 so 15 a 15 30 15 so 15 30 15 30 60 00 100%Modulus, p.s.i 590 620 690 030 475 490 460 480 400 400 280 325 215 21sdul s, psi. 1, 560 1, 570 1, 450 1, 440 1, 370 1, 380 080 1,020 760 810375 510 fl% odu1us, psi- 1, 3.10 1, 410 1, 110 1, 000 Ten 1le. p.s.1 1,750 1, 890 1, 270 1, 340 1, 700 1, 640 1, 700 1, 750 1, 350 1. 440 1,830 1. 85 1. 620 1. 550 Elongatmmpercentn 245 200 185 195 245 230 2 26305 295 426 410 425 450 Hardness, Shore An"- 62 64 63 64 G0 62 60 61 6059 55 55 51 52 Percent Volume Swell 1 148 148 124 124 142 140 143 141153 155 194 100 223 230 PROPERTIES AFTER AGING 168 HOURS A'r 250 F. INOIRGULATING AIR OVEN 200% Modul us, psi- 1, 240 1,150 1, 250 1, 240 1,250 1, 000 050 1, 000 1, 100 1, 100 1. 1B0 05:) 020 Tensue, .s.1. 1, 4501, 500 1, 350 1, 300 1, 570 1, 490 1, 350 1, 200 1, 300 1, 400 1, 250 1,350 1, 175 1, 110 Elongation, pereent .v 265 295 2 215 255 235 275 r 245280 275 225 245 310 320 PROPERTIES AFTER AGING 16 HOURS AT 380 F. INOIRCULATING AIR OVEN 11. i 300 275 200 200 230 160 410 400 250 250 270280 Tens1le, p.s.1 375 350 370 315 250 260 260 240 540 510 320 360 400450 Elongation, pereen 300 390 390 465 500 500 600 555 410 405 500 520460 535 Gyelohexane at 25 C.

The results in Table XII-I show that brominated butyl rubber can besatisfactorily cured with various polythiol compounds in the presence orabsence of a metal oxide. Several of the vulcanizates, particularlyrecipes N, O and R, were strongly resistant to heat.

It is not intended to restrict the present invention to the foregoingexamples which are given to merely demonstrate .of 85 to 99.5 wt.percent of a C to O, isoolefin and to 0.5 wt. percent of a multiolefincontaining 4 to 14 carbon atoms per molecule, said halogenated copolymerbeing chosen from the group consisting of brominated and chlorinatedcopolymers which comprises mixing said rubber with 0.1 to 15 parts byweight per 100 parts of rubber of organic polythiol substance selectedfrom the group consisting of 1,2 ethane dithiol, 1,3 propane dithiol,1,4 butane dithiol, 1,5 pentane dithiol, 1,6 hexane dithiol, glycoldimercaptoacetate, bismercaptomethyl-m-benzene,bismercaptornethyl-m-xylene, bismercaptomethyl durene, 2,4,6mercaptornethyl phenol and 1,2,3 propane trithiol and heating themixture at an elevated temperature.

2. Processfor curing halogenated rubbery copolymer of 85 to 99.5 Wt.percent of a C to C isoolefin and 15 to 0.5 wt. percent of a multiolefincontaining 4 to 14 carbon atoms per molecule, said halogenatedcopolyrner being chosen from the group consisting of brominated andchlorinated copolymers which comprises mixing said rubber with 0.1 to 15parts by weight per 100 parts of rubber of an organic thiol compoundhaving at least two thiol groups selected from the group consisting of1,2 ethane dithiol, 1,3 propane dithiol, 1,4 butane dithiol, 1,5 pentanedithiol, 1,6 hexane dithiol, glycol dimercaptoacetate,bismercaptomethyl-m-benzene, bismercaptomethyl-m-xylene,bismercaptomethyl durene, 2,4,6 mercaptomethyl phenol and 1,2,3 propanetrithiol and heating the mixture to a temperature of 250 F. or more forfrom a few minutes to several hours.

3. Process according to claim 2 in which the thiol compound contains 2to 6 thiol groups.

4. Process for curing halogenated rubbery copolymer of 85 to 99.5 Wt.percent of a C to C7 isoolefin and 15 to 0.5 wt. percent of amultiolefin containing 4 to 14 carbon atoms per molecule, saidhalogenated copolymer being chosen from the group consisting ofbrorninated and chlorinated copolymers which comprises mixing said.rubber with 0.1 to 15 parts by weight per 100 parts of rubber of organicthiol compound having at least two thiol groups, said compound beingselected from the group consisting of 1,2 ethanol dithiol, 1,3 propanedithiol, 1,4 butane dithiol, 1,5 pentane dithiol, 1,6 hexane dithiol,glycol dimercaptoacetate, bismercaptomethyl n1 benzene,bismercaptomethyl-m-xylene, bismercaptomethyl durene, 2,4,6mercaptomethyl phenol and 1,2,3 propane trithiol, and heating themixture at a temperature of 250 F. or more until cured.

5. Process for curing halogenated rubbery copolymers of to 99.5 wt.percent of isobutylene and 15 to 0.5 wt. percent of isoprene, saidhalogenated copolymer being chosen from the group consisting ofbrominated and chlorinated copolymers which comprises mixing said rubberwith 0.5 to 10 parts by weight per 100 parts of rubber of a bivalentmetal oxide and 0.1 to 15 parts by weight per 100 parts of rubber of anorganic thiol compound selected from the group consisting of 1,2 ethanedithiol; 1,3 propane dithiol; 1,4 butane dithiol; 1,5 pentane dithiol;1,6 hexane dithiol; glycol dimercaptoacetate;bismercaptomethyl-m-benzene; bismercaptomethyl-rn-xylene;bismercaptornethyl durene; 2,4,6 mercaptomethyl phenol; and 1,2,3propane trithiol; and heating the mixture at 250 to 400 F. for from afew minutes to several hours.

6. Process according to claim 5 in which the metal in the metal oxide islow melting.

7. Process for curing halogenated rubbery copolymers of 85 to 99.5 wt.percent of isobutylene and 15 to 0.5 wt. percent of a multiolefincontaining 4 to 14 carbon atoms per molecule, said halogenated copolymerbeing chosen from the group consisting of brominated and chlorinatedcopolymers having a mole percent unsaturation of about 0.5 to 15 andcontaining at least about 0.5 wt. percent but not more than 3 atoms ofcombined halogen per double bond in the copolymer, which comprisesmixing 100 parts by weight of said copolymer with from about 0.1 to 15parts by weight of an organic dithiol compound selected from the groupconsisting of 1,2 ethane dithiol; l,3 propane dithiol; 1,4 butanedithiol; 1,5 pentane dithiol; 1,6 hexane dithiol; glycoldimercaptoacetate; bismercaptomethyl-mbenzene;bismercaptomethyl-m-xylene; bismercaptomethyl durene; 2,4,6mercaptomethyl phenol; and 1,2,3 propane trithiol; and about 0.5 to 10parts by weight of bivalent metal oxide and heating the mixture at 250to 400 F. for from 5 to minutes.

8. Process according to claim 7 in which the dithioi compound is a C toC alkyl dithiol.

9. Process according to claim 7 in which the bivalent metal oxide isZinc oxide and the dithiol compound i: glycoldimercaptoacetate.

l0. Vulcanized rubber which comprises a major proportion of halogenatedrubber copolymer of 85 to 99.5 wt

percent of a C to C isoolefin and 15 to 0.5 wt. percent of a multiolefincontaining 4 to 14 carbon atoms per molecule, said halogenated copolymerbeing chosen from the group consisting of brominated and chlorinatedcopolymers and 0.1 to 15 parts by Weight per 100 parts of rubber oforganic polythiol substance chosen from the group consisting of 1,2ethane dithiol, 1,3 propane dithiol, 1,4 butane dithiol, 1,5 pentanedithiol, 1,6 hexane dithiol, glycol dimercaptoacetate, bismercaptomethylIn benzene, bismercaptomethyl-m-Xylene, bismercaptomethyl durene, 2,4,6mercaptomethyl phenol and 1,2,3, propane trithiol.

11. Vulcanized rubber which comprises a major proportion of halogenatedrubbery copolymer of 85 to 99.5 Wt. percent of isohutylene and 15 to 0.5Wt. percent of isoprene, said halogenated copolymer being chosen fromthe group consisting of brominated and chlorinated copoly mers and 0.1to 15 parts by Weight per 101) parts of rubber of organic thiol compoundhaving at least two thiol groups selected from the group consisting of1,2 ethane dithiol,

1,3 propane dithiol, 1,4 butane dithiol, 1,5 pentane dithiol, 1,6 hexaneditbiol, glycol dimercaptoacetate, bismercaptomethyl-m-benzene,bismercaptomethyl-m-xylene, bismercaptornethyl durene, 2,4,6mercaptomethyl phenol and 1,2,3 propane trithiol.

12. Vulcanized rubber according to claim 11 in which the copolymer ischlorinated.

13. Vulcanized rubber according to claim 11 in which the copolyrner isbrominated.

Zimmerman et al.: Handbook of Material Trade Names, Ind. ResearchService, N. H. (1953 edition), page 98.

5. PROCESS FOR CURING HALOGENATED RUBBERY COPOLYMERS OF 85 TO 99.5 WT. PERCENT OF ISOBUTYLENE AND 15 TO 0.5 WT. PERCENT OF ISOPRENE, SAID HALOGENATED COPOLYMER BEING CHOSEN FROM THE GROUP CONSISTING OF BROMINATED AND CHLORINATED COPOLYMERS WHIHC COMPRISES MIXING SAID RUBBER WITH 0.5 TO 10 PARTS BY WEIGHT PER 100 PARTS OF RUBBER OF A BIVALENT METAL OXIDE AND 0.1 TO 15 PARTS BY WEIGHT PER 100 PARTS OF RUBBER OF AN ORGANIC THIOL COMPOUND SELECTED FROM THE GROUP CONSISTING OF 1,2 ETHANE DITHIOL; 1,3 PROPANE DITHIOL; 1,4 BUTANE DITHIOL; 1,5 PENTANE DITHIOL; 1,6 HEXANE DITHIOL; GLYCOL DIMERCAPTOACETATE; BISMERCAPTOMETHYL-M-BENZENE; BISMERCAPTOMETHYL-M-XYLENE; BISMERCAPTOMETHYL DURENE; 2,4,6 MERCAPTOMETHYL OHENOL; AND 1,2,3 PROPANE TRITHIOL; AND HEATING THE MIXTURE AT 520 TO 400*F. FOR FROM A FEW MINUTES TO SEVERAL HOURS. 